Nanoscale heterojunctions of InGaN/GaN photocathodes for electron sources

Abstract

The design of the photocathode is crucial for generating high-quality electron beam in electron sources. In this study, InGaN/GaN heterojunction nanowire photocathodes were proposed, and the photoemission theoretical model was developed. The results demonstrate that the built-in electric field along the axis enables the heterojunction nanowire photocathode to achieve higher collection efficiency across the response spectrum compared to In_0.5Ga_0.5N nanowire photocathodes. The variation of incidence angle results in distinct peaks in quantum efficiency and collection efficiency for the heterojunction nanowire photocathode. Meanwhile, the “additional electric field” has the potential to decrease the number of laterally emitted electrons from the nanowires, consequently reducing the shielding effect of adjacent nanowires. With an incidence angle of 15° and an “additional electric field” of 2 V/μm, the collection efficiency of photoelectrons at the collection end can be maximized to 47.6 %. This indicates that the heterojunction nanowire array photocathode has potential for use in high-performance vacuum electron sources.